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Патент USA US2130869

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Patented Sept. 20, 1938
2,130,869
UNITED STATES
PATENT OFFICE
2,130,869
MANUFACTURE OF NONCAKING POWDER
COIHPOSITION
\
Louis Block and Max Metziger, Joliet, Ill., assign.
ors to Blockson Chemical 00., Joliet, 11]., a cor
poration oi’ Illinois
No Drawing. Application August 7, 1935,
Serial No. 35,103
15 Claims. (or 81-5)
The present invention relates to mixtures of
ingredients in powder form which tend to cake,
and to the avoidance of caking. It has special
reference to mixtures containing silica and tri
5 sodium phosphate.
There are onlthe market many compounds
containing trisodium phosphate which is a mild
alkali. These are used as cleaning compounds,
and in order to give a scouring property to the
10 compound, ?nely divided abrasives are often
added. When silica is present, there is a tend
ency for the powder mixture to cake. The
present invention is based upon ascertaining the
causes of caking, and consists 'in the addition of
15 one or more corrective agents to keep such a
powder mixture in uncaked form.
It has been discovered that the caking is
caused by a chemical reaction involving silica
in the formation of sodium silicate. This is
20 generically the name for various forms of chemi
cal combinations which may originate from caus
tic soda and silica, of which there are both sim—
ple and complex species. The "water glass” of
commerce is a familiar example of sodium sili
25 cate, and it exemplifies an adhesive quality of
sodium silicate, which apparently functions in
the powder mixture above mentioned, as a
cement or adhesive, producing the caking. ‘ The
formation of sodium silicate in the powder mix
30 ture is aided by the presence of water. Water or
moisture may be absorbed by the mixture, or it
may be provided by the water of crystallization
contained in the trisodium phosphate crystals,
for example NaaPOnl2H2O. The caustic soda
35 which is involved in the formation of sodium
silicate may be an impurity in the mixture, for
example, an inclusion in the trisodium phosphate
crystals, or it may be provided by a hydrolysis
4,0
of trisodium phosphate itself.
The primary object of the invention is to mini
mize or prevent the presence of sodium silicate,
thus minimizing or preventing an adhesive or
cementing action, and at the same time to form
a different silicate which does not have a caking
quality.
Another object of the invention is the use in
the mixture of a well distributed aluminum com
pound which is reactive with the solubilized
silica to form a non-caking aluminum-contain
“) ing silicate.
Still another object of the invention is the
addition of a corrective agent consisting of car
rier particles containing only a carried portion
of the active aluminum compound.
;5
A particular object of the invention is the use
of an active aluminum phosphate as the cor
rective agent.
,
Various other and ancillary objects and ad
vantages of the invention will become apparent
from the following description and explanation. 5
In the investigation of the caking of mixtures
of trisodium phosphate and ?nely divided silica
(about 60% passing a 400 mesh screen and about
90% passing a 200 mesh screen) there was em
ployed a standard method of analysis which de- 10
termines soluble silica, or better soluble silicates,
such as of sodium. Since the method involves
use of water, there is bound to be found more
such silicate than is actually present. This ex
cess found by analysis will of course var'y with 15
the procedure and the character of the sample,
for example, with the size of silica and the type
of silica. The excess may be determined rough~
ly in a “blank” analysis on a fresh mixture in
which the caking reaction has not developed, 20
the components of said blank mixture corre
sponding to the components of the mixture to
be tested. Where blank samples may show that
about .05% silica is soluble, a test sample show
ing about .25% soluble silica is one which is 25
de?nitely caked.
'
In studying the effects of various corrective
agents, test mixtures may be exposed to condi
tions which induce the caking reaction. One
suitable way is to subject the samples for a clef- 30
inite period of time to de?nite humidity at de?
nite temperature-then to a normal room tem
perature for a given period-and then to repeat
the alternate exposures for a ?xed number of
times.
35
For example a mixture of 30% trisodium phos
phate (Na3PO4.12H2O) and 70% silica (of mesh
given above) will cake in a ?ber package when
exposed alternately, four times to 105.“ F. and
60% humidity for 3-day periods, andalternately 40
four times to room conditions for three-day
periods. By use of a corrective agent according
to this invention, the same samples can with
stand such a test without caking.
It has been found that compounds containing 45
aluminum can be used which provide aluminum
for the formation of aluminum-containing sili
cate, the latter compound resulting from the re
action which otherwise leads to caking. Not all
aluminum compounds are useful. They must be 50
considered as active or inactive compounds, ac
cording as they function to minimize caking.
Certaincompoundschemically the same in em
pirical formula, may differ in physical form, yet
in one form be active and in another be inactive. 55
2
araaece
phosphates has about 14% to 15% of the latter.
Aluminum phosphate (AJPOQ) is one such
compound. Its refractory and calcined forms
are substantially inactive to prevent caking, while
the dried precipitated and chemically prepared
- (uncalcined) forms, such as amorphous forms,
are active for functioning according to the pres
ent invention. There seems to be no ready rule
of measure, except experience, the test above
described, and like arbitrary test. Therefore,
10 where the'term ‘.‘active” is employed herein, it
refers to those forms which may be used to carry
out the present invention.
Aluminum hydrate (A12O3..’1:H2O) is another
suitable active compound. This may be prepared
by precipitating aluminum hydroxide in a well
known manner and drying the same. One form
is obtainable on the market as “light aluminum
hydrate” used in printing inks, but such com
mercial material is an impure form, more accu
A 70-30 silica-trisodium phosphate mixture can
be cured from caking by the presence of 4% of
such residue containing about 15% aluminum
phosphate. This amounts to about .6% of alu
minum phosphate. This amount so applied gives
a much better correction than the same quantity
of ?nely divided 100% aluminum phosphate. It
requires about 1% of the latter to secure as good
results as with the 4% of impure material above
referred to. 0.5% of 100% aluminum phosphate
is hardly su?icient for practical elimination of
caking in the 70-30 mixture described, but it gives
substantial improvement.
The above details are all given with reference
to the 70-30 mixture described, for the purpose of
illustrating the invention. It is not possible to
state the limits of the invention because an ex
cess does no real harm, and because a minimum
rately known as basic aluminum sulphate, having
a small content of alum (aluminum sulphate)
bound in a complex relation to the aluminum
requirement will be determined by many factors. 20
The character of and the fineness of both silica
and of trisodium phosphate, the character of
hydrate.
package, the conditions of exposure, all have a
bearing on the extent to which the caking re
action may extend.
25
It should of course be understood that one tiny
particle of the corrective agent has a limited
Alum itself is suitable for carrying out the
25 ideas of the invention, but for practical purposes
wherein the cakable mixture is used for its alka
linity, it is not desirable to use an alum or other
‘alum complexes (such as sodium or potassium
alum) which hydrolyze into a slightly acid form.
Organic aluminum compounds also may be
30
active for the purposes of this invention. Alu
minum acetate may be used, and other salts of
organic acids, such as the aluminum soaps, for
example aluminum stearate. For many reasons
35 these are not preferred to others. The active
aluminum phosphate is preferred, and although
sphere of influence in preventing caking. There
fore, in the aggregate, where a limited quantity
of such agent is present, increased ?neness will
extend its total effect. Each particle within its
sphere of in?uence or within its immediate vicin
ity, will prevent caking, and the aggregate e?ect
will be minimizing thecaking of the whole mix
ture. The extent to which “minimizing” will be 35
“prevention” is of course to be determined by
many factors, as will be obvious to one skilled in
‘ it is normally insoluble in water, yet its aluminum
is available for reaction in the presence of alkali.
the art, from the description and explanation
‘Whenever soluble silicate is‘ formed in the pres
here given. For commercial usage mixtures can '
ence of ‘alkali and aluminum phosphate, an alu
minum-containing silicate results, rather than
adhesive sodium silicate. The exact mechanism
of the reaction is not known, but it is certain
that the resulting aluminum-containing silicate
is such that no caking takes place.
It is particularly to be noted that once the
corrective agent is added to a mixture to mini
mize caking it is no longer possible by ordinary
methods to determine soluble silica, or to deter
mine aluminum-containing silicate. The suc
cess of the correcting agent is measurable, in a
practical sense, only in terms of the quantity
used'and in terms'of degree of caking or of non
caking.
55
‘
'
The use of ?nely ground aluminum phosphate
must be such that it is dispersed uniformly and
widely throughout the mixture of silica and tri
sodium phosphate. It must be present every
where in order‘ absolutely to prevent the caking.
60 Of course only its surface can be available for
reaction, and its interior is inert. It is possible
to use ilnely divided particles having a frac
tional content of the active correcting agent, the
body of theparticle being carrier, and the frac
tional content at the surface being available as
a correctingagent. For example where alumi
num ‘phosphate is the desirable correcting agent,
the particles may be residue of miscellaneous
substances, preferably phosphates of metals such
70 as calcium, iron and aluminum. From .many
processes of chemical operations in a plant treat
ing phosphorus compounds, many complex resi
dues-are available with a fractional content of
aluminum phosphate.
75
One useful residue con
sisting largely‘ of_ calcium, iron, and aluminum
betmade substantially non-caking in the aggre 40,
ga e.
'
Heretofore, the art has made the silica very
?ne, in order to minimize the grittiness and
scratching. It has also made the crystals of the
trisodium phosphate very coarse, because this
minimized the caking. This coarseness made the
material ‘more slowly-soluble in use, and there
fore less satisfactory. By reason of the present
invention, both the trisodium phosphate and the
silica may be more ?nely ground and hence the
product be greatly improved without the danger
of caking.
It is to be understood that trisodium phosphate
is obtainable in varying degrees of solubility and
with varying’ impurities. When its crystals are 55
formed, they have a strong tendency to carry
into the crystals, other chemicals associated with
them in the liquor. Thus, some contain under
5% of sodium ?uoride, sodium borate, sodium ni
trate, or sodium hydroxide.
One form contain
ing about 4% of sodium ?uoride, is not readily
soluble‘ One containing caustic soda, a form
commonly used for silica base cleaning mixtures,
is very likely to form cake with great rapidity,
and therefore, the invention is particularly ad 65
vantageous in permitting use of such material,
and in permitting ?ne-grinding of it for the pow
der mixture.
Accordingly the invention contemplates var
70
ious embodiments or compositions which contain
any cakable mixture of trisodium phosphate,
(and of course its less commonly used equivalent
in the other alkali metals, potassium, lithium,
etc.) silica, and an aluminum compound active 75
greases
with such a mixture to minimize the coking, as
de?ned in the appended claims.
We claim:
a
1. The method of minimizing caking of a pow
dery physical mixture oi’ particles of silica and
of particles of trisodium phosphate which com
prises thoroughly dispersing throughout the mix
ture a small quantity of an aluminum compound
which is active to prevent in its immediate vicin
ity the formation of an adhesive substance caus
ing caking, said adhesive being normally caused
by interaction of silica. and alkaline sodium com
pound derived from the particles of trisodium
phosphate.
15
2. The method of minimizing coking of a pow
dery physical mixture of particles of, silica and
of particles of trisodium phosphate which com
prises thoroughly dispersing throughout the mix
ture a small quantity of particles consisting sub
20 stantially of an aluminum compound which is
active to prevent in its immediate vicinity the
formation of an adhesive substance causing cak
ing, said adhesive substance being normally
caused by interaction of silica and alkaline so
25 dium compound derived from the particles of
trisodium phosphate.
.
3. The method of minimizing caking of a pow
dery physical mixture of particles of silica and
of particles of trisodium phosphate which com
30 prises thoroughly dispersing throughout the mix
ture a small quantity of particles containing a
fractional content of an aluminum compound
which is active to prevent in its immediate vicin
ity the formation of an adhesive substance caus
35 ing caking, said adhesive substance being nor
mally caused by interaction of silica and alkaline
sodium compound derived from the particles of
trisodium phosphate.
4. The method of minimizing calring of a pow
40 dery physical mixture of particles of silica and
of particles of trisodium phosphate which com
prises thoroughly dispersing throughout the mix
ture a small quantity of particles of aluminum
phosphate which is active to prevent in its imme
45 diate vicinity the formation of an adhesive sub
50
3
dery physical mixture of particles of silica and of
particles of trisodium phosphate which include
as an impurity of crystallization a small quan
tity of alkaline sodium compound in the form
of caustic soda, which comprises thoroughly dis
persing throughout the mixture :2. small quan
tity of an aluminum compound which is active
to prevent in its immediate vicinity the formation
of an adhesive substance causing caking, said ad
hesive substance being normally caused by inter 1%
action of silica and alkaline sodium compound
derived from the particles of trisodium phos
phate.
8. The method of minimizing caking of a pow
. dery physical mixture of particles of silica and of 15
particles of normal phosphate salt of alkali
metal which comprises thoroughly dispersing
throughout the mixture a small quantity of an
aluminum compound which-is active to prevent in
its immediate vicinity the formation of an ad 20
hesive substance causing caking, said adhesive
substance being normally caused by interaction
of silica and alkaline alkali-metal compound de
rived from the particles of said, phosphate salt of
alkali metal.
25
9. A substantially non-coking powdery mix
ture comprising as the essential ingredients par
ticles of silica, particles of the normal alkali
metal phosphate salt, and a small quantity-of
aluminum compound which is active to prevent
in its immediate vicinity the formation of an
adhesive substance which is the cause of caking,
said adhesive substance being normally formed
by interaction between silica and alkaline com
pound derived from particles of the said phos
phate salt.
35
.
10. A substantially non-coking powdery mix
ture comprising as the essential ingredients par
ticles of silica, particles of trisodium phosphate.
and a small quantity of an aluminum compound
which is active to prevent in its immediate vicin
ity the formation of an adhesive substance which
is the cause of caklng, said adhesive substance
being normally formed by interaction of ‘silica
and alkaline sodium compound derived from the
stance causing caking, said adhesive substance
being normally caused by interaction of silica
and alkaline sodium compound derived from the
particles of trisodium phosphate.
particles of-‘the trisodium phosphate.
11. A substantially non-caking powdery mix
dery physical mixture of particles of silica and
of particles of trisodium phosphate which com
and particles of an aluminum compound which is 50
active to prevent in its immediate vicinity the
formation of an adhesive substance which is the
cause of caking, said adhesive substance being
normally formed by interaction’ of silica and alka
line sodium compound derived from the particles 55
ture comprising as the essential ingredients par
.5. The method of minimizing caking of a pow- I ticles of silica, particles of trisodium phosphate,
prises thoroughly dispersing throughout the mix
ture a small quantity of particles containing a
55 fractional content of aluminum phosphate which
is active to prevent in its immediate vicinity the
formation of an adhesive substance causing
caking, said adhesive substance being normally
caused by interaction of silica and alkaline so
dium compound derived from the particles of
trisodium phosphate.
6. The method of minimizing caking of a pow
dery physical mixture of particles of silica and
of particles of trisodium phosphate which in
of the trisodium phosphate.
12. A substantially non-caking powdery mix~
ture comprising as the essential ingredients par
ticles of silica, particles of trisodium phosphate,
and particles of aluminum phosphate which is ac 60
tive to prevent in its immediate vicinity the for
quantity of alkaline sodium compound, which
mation of an adhesive substance which is the
cause of caking, said adhesive substance being
normally formed by interaction of silica and al
kaline sodium compound derived from the par 65
comprises thoroughly dispersing throughout the
ticles of the trisodium phosphate.
65 clude as an impurity of crystallization a small
mixture 2. small quantity of an aluminum com
pound which is active to prevent in its immedi
70 ate vicinity the formation of an adhesive sub
stance causing caking, said adhesive substance
being normally caused by interaction of silica
and alkaline sodium compound derived from the
particles of trisodium phosphate.
7. The method of minimizing caking of a pow
75
'
13. A substantially nongoaking powdery mix
ture comprising as the essential ingredients par
ticles of silica, particles of trisodium phosphate, 70
and particles containing a fractional content of
an aluminum compound which is active to pre
vent in its immediate vicinity the formation of
an adhesive substance which is the cause of oak
ing, said adhesive substance being normally 75
areaeee
formed by interaction of silica end alkaline sodi
compound derived from the particles of the
trisodium phosphate.
1a. A substantially non-caking powdery mix
ture comprising as the essential ingredients par
ticles of silica, particles of trisodium phosphate,
and particles containing a fractional content of
aluminum phosphate which is active to prevent in
its
edlate vicinity the formation of an ad
10 hesive substance which is the cause of caking,
said adhesive substance being normally formed
15. A detergent composition consisting of a
physical mixture of particles of silica, particles of
trisodium phosphate crystals, and particles ‘con
taining aluminum phosphate which is active to
prevent the formation in its immediate vicinity
of an adhesive substance which causes caking,
said adhesive substance being formed in the ab
sence of said aluminum phosphate by interaction
between the particles of silica and the substance
derived from the particles of trisodium phos-- 1(11
phate.
'
-
by interaction of silica and alkaline sodium com
pound derived from the particles of the trisodium
phosphate.
LOUIS BLOCK.
METZIG iiRf’l
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